With the very latest and best Eddy Current Test equipment we offer in-house and on-site Testing to all industry sectors. Our reliable and accurate testing service has won significant contracts from major companies around the world.
Mainly used by our clients as an on-site service by NFW Inspection Co Ltd we do also offer an in-house service. Eddy current services are offered to clients from many sectors of industry including Aerospace, Motorsport, film and television, Military and many others. Our rapid response service offered by our incident response team can put a technician where one is needed fast anywhere in the UK and Europe. Our highly skilled team of technicians are always on hand to give help and advice.
In its most basic form — the single-element ECT probe — a coil of conductive wire is excited with an alternating electrical current.
This wire coil produces an alternating magnetic field around itself in the direction ascertained by the right-hand rule. The magnetic field oscillates at the same frequency as the current running through the coil.
When the coil approaches a conductive material, currents opposed to the ones in the coil are induced in the material — eddy currents.
Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a tell-tale sign of the presence of defects. This is the basis of standard (pancake coil) ECT.
ECT has a very wide range of applications. Because ECT is electrical in nature, it is limited to conductive material.
There are also physical limits to generating eddy currents and depth of penetration (skin depth).
inspections. Surface inspection is used extensively in the aerospace industry. The technique is very sensitive and can detect tight cracks. Surface inspection can be performed both on ferromagnetic and non-ferromagnetic materials.
Tubing inspection is generally limited to non-ferromagnetic tubing and is known as conventional eddy current testing. Conventional ECT is used for inspecting steam generator tubing in nuclear plants and heat exchangers tubing in power and petrochemical industries. The technique is very sensitive to detect and size pits. Wall loss or corrosion can be detected but sizing is not accurate.
A variation of conventional ECT for partially magnetic materials is full saturation ECT. In this technique, permeability variations are suppressed by applying a magnetic field. The saturation probes contain conventional eddy current coils and magnets. This inspection is used on partially ferromagnetic materials such as nickel alloys, duplex alloys, and thin-ferromagnetic materials such as ferritic chromium molybdenum stainless steel. The application of a saturation eddy current technique depends on the permeability of the material, tube thickness, and diameter.
A method used for carbon steel tubing is remote field eddy current testing. This method is sensitive to general wall loss and not sensitive to small pits and cracks